Get rid of MSVC problems and improve state API.

- Just let MSVC have crap codegen. The compiler sucks anyways. Fixes
- Add incremental GC power. Fixes #997.
- Add non-null offset manipulation. Did I mention I hate VC++ and how it implemented _Aligned? Fixes #1017.

include/sol/function_types_stateless.hpp

@@ -28,14 +28,19 @@
 #include <sol/call.hpp>
 #include <sol/bind_traits.hpp>
 
-namespace sol {
+namespace sol { namespace function_detail {
-namespace function_detail {
 	template <typename Function, bool is_yielding>
 	struct upvalue_free_function {
 		using function_type = std::remove_pointer_t<std::decay_t<Function>>;
 		using traits_type = meta::bind_traits<function_type>;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			auto udata = stack::stack_detail::get_as_upvalues<function_type*>(L);
 			function_type* fx = udata.first;
 			return call_detail::call_wrapped<void, true, false>(L, fx);
@@ -61,7 +66,13 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member function pointer
 			// idx n + 1: is the object's void pointer
@@ -72,7 +83,13 @@ namespace function_detail {
 			return call_detail::call_wrapped<T, true, false, -1>(L, memfx, item);
 		}
 
-		static int call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -92,7 +109,13 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member variable pointer
 			// idx n + 1: is the object's void pointer
@@ -112,7 +135,13 @@ namespace function_detail {
 			}
 		}
 
-		static int call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -132,7 +161,13 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member variable pointer
 			// idx n + 1: is the object's void pointer
@@ -150,7 +185,13 @@ namespace function_detail {
 			}
 		}
 
-		static int call(lua_State* L) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -170,14 +211,26 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member variable pointer
 			function_type& memfx = stack::get<user<function_type>>(L, upvalue_index(2));
 			return call_detail::call_wrapped<T, false, false>(L, memfx);
 		}
 
-		static int call(lua_State* L) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -258,7 +311,6 @@ namespace function_detail {
 			return call(L);
 		}
 	};
-}
+}} // namespace sol::function_detail
-} // namespace sol::function_detail
 
 #endif // SOL_FUNCTION_TYPES_STATELESS_HPP

include/sol/stack_core.hpp

@@ -92,7 +92,9 @@ namespace sol {
 
 		template <typename... Args>
 		std::size_t aligned_space_for(void* alignment = nullptr) {
-			char* start = static_cast<char*>(alignment);
+			// use temporary storage to prevent strict UB shenanigans
+			char alignment_shim[(std::max)({ sizeof(Args)... }) + (std::max)({ alignof(Args)... })] {};
+			char* start = alignment == nullptr ? static_cast<char*>(alignment) : alignment_shim;
 			(void)detail::swallow { int {}, (align_one(std::alignment_of_v<Args>, sizeof(Args), alignment), int {})... };
 			return static_cast<char*>(alignment) - start;
 		}

include/sol/state_view.hpp

@@ -637,10 +637,88 @@ namespace sol {
 			return s;
 		}
 
+		bool supports_gc_mode(gc_mode mode) const noexcept {
+#if SOL_LUA_VERSION >= 504
+			// supports all modes
+			(void)mode;
+			return true;
+#endif
+			return mode == gc_mode::default;
+		}
+
+		bool is_gc_on() const {
+			return lua_gc(lua_state(), LUA_GCISRUNNING, 0) == 1;
+		}
+
 		void collect_garbage() {
 			lua_gc(lua_state(), LUA_GCCOLLECT, 0);
 		}
 
+		void collect_gc() {
+			collect_garbage();
+		}
+
+		bool step_gc(int step_size_kilobytes) {
+			// THOUGHT: std::chrono-alikes to map "kilobyte size" here...?
+			// Make it harder to give MB or KB to a B parameter...?
+			// Probably overkill for now.
+#if SOL_LUA_VERSION >= 504
+			// The manual implies that this function is almost always successful...
+			// is it?? It could depend on the GC mode...
+			return lua_gc(lua_state(), LUA_GCSTEP, step_size_kilobytes) != 0;
+#else
+			return lua_gc(lua_state(), LUA_GCSTEP, step_size_kilobytes) == 1;
+#endif
+		}
+
+		void restart_gc() {
+			lua_gc(lua_state(), LUA_GCRESTART, 0);
+		}
+
+		void stop_gc() {
+			lua_gc(lua_state(), LUA_GCSTOP, 0);
+		}
+
+		// Returns the old GC mode. Check support using the supports_gc_mode function.
+		gc_mode change_gc_mode_incremental(int pause, int step_multiplier, int step_byte_size) {
+			// "What the fuck does any of this mean??"
+			// http://www.lua.org/manual/5.4/manual.html#2.5.1
+
+			// THOUGHT: std::chrono-alikes to map "byte size" here...?
+			// Make it harder to give MB or KB to a B parameter...?
+			// Probably overkill for now.
+#if SOL_LUA_VERSION >= 504
+			int old_mode = lua_gc(lua_state(), LUA_GCINC, pause, step_multiplier, step_byte_size);
+			if (old_mode == LUA_GCGEN) {
+				return gc_mode::generational;
+			}
+			else if (old_mode == LUA_GCINC) {
+				return gc_mode::incremental;
+			}
+#else
+			lua_gc(lua_state(), LUA_GCSETPAUSE, pause);
+			lua_gc(lua_state(), LUA_GCSETSTEPMUL, step_multiplier);
+			(void)step_byte_size; // means nothing in older versions
+#endif
+			return gc_mode::default;
+		}
+
+		// Returns the old GC mode. Check support using the supports_gc_mode function.
+		gc_mode change_gc_mode_generational(int minor_multiplier, int major_multiplier) {
+#if SOL_LUA_VERSION >= 504
+			// "What does this shit mean?"
+			// http://www.lua.org/manual/5.4/manual.html#2.5.2
+			int old_mode = lua_gc(lua_state(), LUA_GCGEN, minor_multiplier, major_multiplier);
+			if (old_mode == LUA_GCGEN) {
+				return gc_mode::generational;
+			}
+			else if (old_mode == LUA_GCINC) {
+				return gc_mode::incremental;
+			}
+#endif
+			return gc_mode::default;
+		}
+
 		operator lua_State*() const {
 			return lua_state();
 		}

include/sol/types.hpp

@@ -646,6 +646,12 @@ namespace sol {
 		file = LUA_ERRFILE,
 	};
 
+	enum class gc_mode : int {
+		incremental = 0,
+		generational = 1,
+		default = incremental,
+	};
+
 	enum class type : int {
 		none = LUA_TNONE,
 		lua_nil = LUA_TNIL,

single/include/sol/config.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2020-08-12 23:04:25.864654 UTC
+// Generated 2020-09-05 21:23:26.771012 UTC
-// This header was generated with sol v3.2.1 (revision 5bbc095)
+// This header was generated with sol v3.2.1 (revision de87bec)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_CONFIG_HPP

single/include/sol/forward.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2020-08-12 23:04:25.839654 UTC
+// Generated 2020-09-05 21:23:26.767014 UTC
-// This header was generated with sol v3.2.1 (revision 5bbc095)
+// This header was generated with sol v3.2.1 (revision de87bec)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_FORWARD_HPP

single/include/sol/sol.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2020-08-12 23:04:25.317593 UTC
+// Generated 2020-09-05 21:23:26.587015 UTC
-// This header was generated with sol v3.2.1 (revision 5bbc095)
+// This header was generated with sol v3.2.1 (revision de87bec)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_HPP
@@ -7079,6 +7079,12 @@ namespace sol {
 		file = LUA_ERRFILE,
 	};
 
+	enum class gc_mode : int {
+		incremental = 0,
+		generational = 1,
+		default = incremental,
+	};
+
 	enum class type : int {
 		none = LUA_TNONE,
 		lua_nil = LUA_TNIL,
@@ -9722,7 +9728,11 @@ namespace sol {
 
 		template <typename... Args>
 		std::size_t aligned_space_for(void* alignment = nullptr) {
-			char* start = static_cast<char*>(alignment);
+			// use temporary storage to prevent strict UB shenanigans
+			using union_type = std::aligned_union<1, Args...>;
+			using union_type_t = typename union_type::type;
+			char alignment_shim[(std::max)({ sizeof(Args)... }) + (std::max)({ alignof(Args)... })] {};
+			char* start = alignment == nullptr ? static_cast<char*>(alignment) : alignment_shim;
 			(void)detail::swallow { int {}, (align_one(std::alignment_of_v<Args>, sizeof(Args), alignment), int {})... };
 			return static_cast<char*>(alignment) - start;
 		}
@@ -17455,14 +17465,19 @@ namespace sol {
 
 // beginning of sol/function_types_stateless.hpp
 
-namespace sol {
+namespace sol { namespace function_detail {
-namespace function_detail {
 	template <typename Function, bool is_yielding>
 	struct upvalue_free_function {
 		using function_type = std::remove_pointer_t<std::decay_t<Function>>;
 		using traits_type = meta::bind_traits<function_type>;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			auto udata = stack::stack_detail::get_as_upvalues<function_type*>(L);
 			function_type* fx = udata.first;
 			return call_detail::call_wrapped<void, true, false>(L, fx);
@@ -17488,7 +17503,13 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member function pointer
 			// idx n + 1: is the object's void pointer
@@ -17499,7 +17520,13 @@ namespace function_detail {
 			return call_detail::call_wrapped<T, true, false, -1>(L, memfx, item);
 		}
 
-		static int call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -17519,7 +17546,13 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member variable pointer
 			// idx n + 1: is the object's void pointer
@@ -17539,7 +17572,13 @@ namespace function_detail {
 			}
 		}
 
-		static int call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -17559,7 +17598,13 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member variable pointer
 			// idx n + 1: is the object's void pointer
@@ -17577,7 +17622,13 @@ namespace function_detail {
 			}
 		}
 
-		static int call(lua_State* L) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -17597,14 +17648,26 @@ namespace function_detail {
 		typedef std::remove_pointer_t<std::decay_t<Function>> function_type;
 		typedef lua_bind_traits<function_type> traits_type;
 
-		static int real_call(lua_State* L) noexcept(traits_type::is_noexcept) {
+		static int real_call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			// Layout:
 			// idx 1...n: verbatim data of member variable pointer
 			function_type& memfx = stack::get<user<function_type>>(L, upvalue_index(2));
 			return call_detail::call_wrapped<T, false, false>(L, memfx);
 		}
 
-		static int call(lua_State* L) {
+		static int call(lua_State* L)
+#if SOL_IS_ON(SOL_COMPILER_VCXX_I_)
+		// MSVC is broken, what a surprise...
+#else
+			noexcept(traits_type::is_noexcept)
+#endif
+		{
 			int nr = detail::typed_static_trampoline<decltype(&real_call), (&real_call)>(L);
 			if (is_yielding) {
 				return lua_yield(L, nr);
@@ -17685,8 +17748,7 @@ namespace function_detail {
 			return call(L);
 		}
 	};
-}
+}} // namespace sol::function_detail
-} // namespace sol::function_detail
 
 // end of sol/function_types_stateless.hpp
 
@@ -25366,10 +25428,88 @@ namespace sol {
 			return s;
 		}
 
+		bool supports_gc_mode(gc_mode mode) const noexcept {
+#if SOL_LUA_VERSION >= 504
+			// supports all modes
+			(void)mode;
+			return true;
+#endif
+			return mode == gc_mode::default;
+		}
+
+		bool is_gc_on() const {
+			return lua_gc(lua_state(), LUA_GCISRUNNING, 0) == 1;
+		}
+
 		void collect_garbage() {
 			lua_gc(lua_state(), LUA_GCCOLLECT, 0);
 		}
 
+		void collect_gc() {
+			collect_garbage();
+		}
+
+		bool step_gc(int step_size_kilobytes) {
+			// THOUGHT: std::chrono-alikes to map "kilobyte size" here...?
+			// Make it harder to give MB or KB to a B parameter...?
+			// Probably overkill for now.
+#if SOL_LUA_VERSION >= 504
+			// The manual implies that this function is almost always successful...
+			// is it?? It could depend on the GC mode...
+			return lua_gc(lua_state(), LUA_GCSTEP, step_size_kilobytes) != 0;
+#else
+			return lua_gc(lua_state(), LUA_GCSTEP, step_size_kilobytes) == 1;
+#endif
+		}
+
+		void restart_gc() {
+			lua_gc(lua_state(), LUA_GCRESTART, 0);
+		}
+
+		void stop_gc() {
+			lua_gc(lua_state(), LUA_GCSTOP, 0);
+		}
+
+		// Returns the old GC mode. Check support using the supports_gc_mode function.
+		gc_mode change_gc_mode_incremental(int pause, int step_multiplier, int step_byte_size) {
+			// "What the fuck does any of this mean??"
+			// http://www.lua.org/manual/5.4/manual.html#2.5.1
+
+			// THOUGHT: std::chrono-alikes to map "byte size" here...?
+			// Make it harder to give MB or KB to a B parameter...?
+			// Probably overkill for now.
+#if SOL_LUA_VERSION >= 504
+			int old_mode = lua_gc(lua_state(), LUA_GCINC, pause, step_multiplier, step_byte_size);
+			if (old_mode == LUA_GCGEN) {
+				return gc_mode::generational;
+			}
+			else if (old_mode == LUA_GCINC) {
+				return gc_mode::incremental;
+			}
+#else
+			lua_gc(lua_state(), LUA_GCSETPAUSE, pause);
+			lua_gc(lua_state(), LUA_GCSETSTEPMUL, step_multiplier);
+			(void)step_byte_size; // means nothing in older versions
+#endif
+			return gc_mode::default;
+		}
+
+		// Returns the old GC mode. Check support using the supports_gc_mode function.
+		gc_mode change_gc_mode_generational(int minor_multiplier, int major_multiplier) {
+#if SOL_LUA_VERSION >= 504
+			// "What does this shit mean?"
+			// http://www.lua.org/manual/5.4/manual.html#2.5.2
+			int old_mode = lua_gc(lua_state(), LUA_GCGEN, minor_multiplier, major_multiplier);
+			if (old_mode == LUA_GCGEN) {
+				return gc_mode::generational;
+			}
+			else if (old_mode == LUA_GCINC) {
+				return gc_mode::incremental;
+			}
+#endif
+			return gc_mode::default;
+		}
+
 		operator lua_State*() const {
 			return lua_state();
 		}
@@ -26275,7 +26415,8 @@ namespace sol {
 		using base_t = std::vector<object, Al>;
 
 	public:
-		basic_variadic_results() : base_t() {}
+		basic_variadic_results() : base_t() {
+		}
 
 		basic_variadic_results(unsafe_function_result fr) : base_t() {
 			this->reserve(fr.return_count());